<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<svg width="800" height="1000"></svg>
<script src="js/d3.v7.js"></script>
<script>
    // 定义JSON数据
    var data = {
        "nodes": [
            {"id": 1, "label": "节点1"},
            {"id": 2, "label": "节点2"},
            {"id": 3, "label": "节点3"}
        ],
        "links": [
            {"source": 1, "target": 2},
            {"source": 2, "target": 3}
        ]
    };

    // 设置图表布局
    var width = 640,
        height = 480;

    var svg = d3.select("body")
        .append("svg")
        .attr("width", width)
        .attr("height", height);

    var color = d3.scaleOrdinal(d3.schemeCategory20);

    // 创建力导向布局
    var simulation = d3.forceSimulation()
        .force("link", d3.forceLink().id(function(d) { return d.id; }))
        .force("charge", d3.forceManyBody())
        .force("center", d3.forceCenter(width / 2, height / 2));

    // 渲染节点和连接
    var link = svg.append("g")
        .attr("class", "links")
        .selectAll("line")
        .data(data.links)
        .enter().append("line")
        .attr("stroke-width", 2);

    var node = svg.append("g")
        .attr("class", "nodes")
        .selectAll("circle")
        .data(data.nodes)
        .enter().append("circle")
        .attr("r", 8)
        .attr("fill", function(d) { return color(d.id); })
        .call(d3.drag()
            .on("start", dragstarted)
            .on("drag", dragged)
            .on("end", dragended));

    node.append("title")
        .text(function(d) { return d.label; });

    simulation
        .nodes(data.nodes)
        .on("tick", ticked);

    simulation.force("link")
        .links(data.links);

    function ticked() {
        link
            .attr("x1", function(d) { return d.source.x; })
            .attr("y1", function(d) { return d.source.y; })
            .attr("x2", function(d) { return d.target.x; })
            .attr("y2", function(d) { return d.target.y; });

        node
            .attr("cx", function(d) { return d.x; })
            .attr("cy", function(d) { return d.y; });
    }

    function dragstarted(d) {
        if (!d3.event.active) simulation.alphaTarget(0.3).restart();
        d.fx = d.x;
        d.fy = d.y;
    }

    function dragged(d) {
        d.fx = d3.event.x;
        d.fy = d3.event.y;
    }

    function dragended(d) {
        if (!d3.event.active) simulation.alphaTarget(0);
        d.fx = null;
        d.fy = null;
    }
</script>
</body>
</html>